Comparison of the metallicity distribution as a function of H I column density for quasar and GRB absorbers with C I or H₂ detections. Blue filled circles again denote the GRBs with C I detected in absorption (empty blue circles show the GRBs with C I detected below the completeness limit). Overplotted are the quasar absorbers with H₂ detections from the VLT/UVES sample (dark red squares), quasar absorbers selected for the presence of the 2175 Å dust extinction feature (green diamonds) and quasar absorbers selected for the presence of C I absorption (yellow squares). Only systems with W_r(λ 1560)> 0.2 Å from each of the C I samples are shown. The dashed lines mark constant values of logN(H I)/cm⁻² + [X/H] as indicated at each line.